This invention relates to a receiving beamformer capable of simultaneously generating a plurality of receiving beam signals corresponding to the receive beams of a plurality of directions on the basis of a plurality of ultrasonic received signals, and an ultrasonic imaging system, such as an ultrasonic diagnosis equipment, ultrasonic reflectoscope or ultrasonic sonar, which uses this receiving beamformer.
The recent ultrasonic imaging system simultaneously generates a plurality of receiving beam signals corresponding to a plurality of receiving beams of different directions for a single round of ultrasonic wave transmission and reception in order to make high-speed imaging. As this kind of technique, an ultrasonic diagnosis equipment is disclosed in, for example, JP-A-59-49752. FIG. 7 shows the receive beamformer 1 used in this ultrasonic diagnosis equipment. Referring to FIG. 7, there are shown variable amplifiers 2, A/D converters 3, digital delay units 4 and adders 5a, 5b. The variable amplifiers 2 amplify, in accordance with the depth of measurement, the signals S.sub.1, S.sub.2, . . . S.sub.n which are received on respective channels by an array of vibrator elements of an ultrasonic transmitter/receiver. The output signals from the variable amplifiers 2 are converted into digital signals by the A/D converters 3. The digital signals from the A/D converters 3 are supplied to and arbitrarily delayed by the digital delay units 4, which then produce a plurality of delayed signals Da.sub.1, Db.sub.1, Da.sub.2, Db.sub.2, . . . , Da.sub.n, Db.sub.n. The delayed signals Da.sub.1, Da.sub.2, . . . , Da.sub.n are supplied to and added by the adder 5a, and the delayed signals Db.sub.1, Db.sub.2, . . . , Db.sub.n supplied to and added by the adder 5b. As a result of addition, a plurality of adders 5a, 5b simultaneously produce the receiving beam signals Ba, Bb corresponding to the receiving beam signals of a plurality of directions. Each of the digital delay units 4 is formed of a shift register 6 and a plurality of parallel multiplexers 7a, 7b. Each signal delay block, 8.sub.1, 8.sub.2, . . . , 8.sub.n, including the variable amplifier 2, the A/D converter 3 and the digital delay unit 4 is provided on each channel for the received signal S.sub.1 through S.sub.n.
The unit delay time necessary for the generation of receiving beam signals Ba, Bb is selected to be, for example, 10 ns. The A/D converters 3 sample the signals S.sub.1 through S.sub.n at a frequency of, for example, 100 MHz, and supply the sampled signals to the shift registers 6 of the respective digital delay units 4. The tap outputs of each of the shift registers 6 are fed to a plurality of the following multiplexers 7a, 7b, which select delay taps corresponding to a plurality of ultrasonic beams of different directions. The multiplexers of the blocks produce the delayed signals Da.sub.1, Db.sub.1, . . . , Da.sub.n, Db.sub.n, which are then supplied to a plurality of adders 5a, 5b, respectively. As a result of addition, the adders produce the receiving beam signals Ba, Bb of a plurality of directions.